The present invention relates to a bridge sleeve that itself can be air mounted to the mandrel of a printing machine in the flexographic or rotogravure printing field and that permits air mounting of a printing cylinder onto the bridge sleeve.
In the flexographic or rotogravure printing field, it is known to use an adapter sleeve (aka bridge sleeve) that is disposed between a rotary mandrel of the printing machine and an actual printing cylinder carrying the data and/or images that are to be printed. The use of an adapter sleeve such as disclosed in commonly owned U.S. Pat. No. 5,782,181, which is hereby incorporated herein in its entirety for all purposes, enables various print developments to be achieved with the same rotary mandrel, without the need to replace this latter (generally of steel, hence costly and heavy) following a change in print development compared with the previous work carried out on the same printing machine.
Various methods are known for mounting a conventional adapter sleeve (defined by a hollow cylinder with a through hole) onto a rotary mandrel of a printing machine. While mounting systems employing hydraulics and mounting systems employing mechanical connections are known, these typically are more cumbersome and heavier than a much used “air mounting” system in which a conventional adapter sleeve that has an inner surface diameter slightly smaller than the diameter of the outer surface of the mandrel. The difference between these diameters enables an interference fit to be achieved between the mandrel of the printing machine and the conventional adapter sleeve. Positioning the conventional adapter sleeve at one end of the mandrel, compressed air is supplied (by known methods) between the outer surface of the mandrel and the inner surface of the adapter sleeve. The compressed air expands the inner surface of the conventional adapter sleeve sufficiently to allow the adapter sleeve to slide over a cushion of air onto the mandrel. When the supply of compressed air is ended, the inner surface of the conventional adapter sleeve shrinks and grips the outer surface of the mandrel in an interference fit between the mandrel and the conventional adapter sleeve. Similarly, by again feeding compressed air onto the mandrel surface, the conventional adapter sleeve can be slightly widened to enable it to be released from the interference fit and removed from the mandrel.
Air-mountable adapter sleeves such as disclosed in commonly owned U.S. Pat. Nos. 5,819,657; 6,688,226; and 6,691,614, each of which being hereby incorporated herein in its entirety for all purposes, is usually made with a multi-layer body comprising at least one elastically compressible and radially deformable layer running the length of the adapter sleeve. The compressed air acting against the inner surface of such an adapter sleeve compresses this elastically compressible and radially deformable layer, which can be made of polyurethane foam, to enable the inner surface of the adapter sleeve to expand radially as it is being mounted on the outer surface of the mandrel.
However this elastic characteristic, although enabling the conventional adapter sleeve to be air-mounted on the mandrel, works at cross purposes with the need for the adapter sleeve's outer surface to remain as rigidly fixed as possible with respect to the mandrel of the printing machine in order to resist the vibrations that are generated during operation of the printing machine. When the mandrel of such a printing machine rotates at speeds necessary to advance the substrate through the printing machine at line speeds of more than about 250 meters/minute, the presence of the elastically compressible and radially deformable layer in a conventional adapter sleeve permits the machine vibrations to cause radial displacements of the adapter sleeve's outer surface with respect to the mandrel. These radial displacements are more likely to arise the larger the sleeve's length and diameter. When these radial displacements do arise, they compromise print quality to an unacceptable level by causing banding or skipping. Nonetheless, printing machines that generate line speeds exceeding 250 meters/minute are becoming the norm, and a need exists for air-mountable adapter sleeves that produce acceptable print quality.
When a conventional adapter sleeve is mounted on the mandrel of a printing machine, it becomes possible to draw the printing cylinder onto the outer surface of this conventional adapter sleeve by feeding pressurized air beneath the printing cylinder in a manner similar to the mounting of the inner surface of the adapter sleeve onto the outer surface of the printing machine's mandrel. Depending on the way that a conventional adapter sleeve supplies pressurized air to the adapter sleeve's outer surface and beneath the printing cylinder, the conventional adapter sleeve can be classified by either the designation “piped” or the designation “flow through.”
A piped adapter sleeve receives the pressurized air via a connector that is fitted to the adapter sleeve during mounting of the printing sleeve and then disconnected from the adapter sleeve before the printing process begins. The pressurized air reaches the outer surface of the piped adapter sleeve through one or more conduits that run axially through the adapter sleeve before being connected to holes through the outer surface of the adapter sleeve.
A flow through adapter sleeve has a plurality of through holes, which may open for example into its inner surface, but always open into its outer surface. The through holes receive the pressurized air from the printing machine's mandrel. This transfer of pressurized air from the mandrel to the adapter sleeve can be accomplished in several ways known in the art. For example, a groove can be defined circumferentially in the outer surface of the mandrel so as to be positioned beneath the through holes in the adapter sleeve. Pressurized air from within the mandrel is supplied via at least one hole emptying into the groove in the mandrel. Alternatively, a groove can be defined circumferentially in the inner surface of the adapter sleeve so as to be positioned above the through holes in the mandrel (or the groove in the mandrel) from which pressurized air is supplied and thence to the through holes in the adapter sleeve. Moreover, any of the foregoing groove and hole arrangements can be supplied on only one end of the adapter sleeve and on one end of the mandrel or alternatively can be provided on both ends of the adapter sleeve and/or the mandrel.